Hi Julio, You can use a factor to index another object just as you'd use any other index: > incomes[statef == "act"] [1] 46 43
It looks like you're using the R intro guide, but there's a lot of other material available. Try this one for starters: http://www.stat.berkeley.edu/classes/s133/factors.html Is there something specific you're trying to accomplish? Sarah On Fri, Mar 30, 2012 at 12:50 PM, Julio Sergio <julioser...@gmail.com> wrote: > > I'm trying to figure out about factors, however the on-line documentation is > rather sparse. I guess, factors are intended for grouping arrays members into > categories, which R names "Levels". And so we have: > > * state <- c("tas", "sa", "qld", "nsw", "nsw", "nt", "wa", "wa", > "qld", "vic", "nsw", "vic", "qld", "qld", "sa", "tas", > "sa", "nt", "wa", "vic", "qld", "nsw", "nsw", "wa", > "sa", "act", "nsw", "vic", "vic", "act") > * statef <- factor(state) > * statef > [1] tas sa qld nsw nsw nt wa wa qld vic nsw vic qld qld sa tas sa nt > wa > [20] vic qld nsw nsw wa sa act nsw vic vic act > Levels: act nsw nt qld sa tas vic wa > > With this, just visually, I know what the cateogries or Levels are. > Nonetheless, > two questions arise here: How can I have, computationally as opposed to > visually, access to the names of these categories, and how do I get the > indexes > of the original array elements that belong to a particular category, say, > "act"? > This is, for instance, to select from another "parallel" array, the > corresponding elements, say > > > * incomes <- c(60, 49, 40, 61, 64, 60, 59, 54, 62, 69, 70, 42, 56, > 61, 61, 61, 58, 51, 48, 65, 49, 49, 41, 48, 52, 46, > 59, 46, 58, 43) > > So to select, the corresponding elements to "act": > > 46 43 > > > Do you have any comments on this? > > Thanks, > > --Sergio. > -- Sarah Goslee http://www.functionaldiversity.org ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
